Current sensing and motor control

Abstract

A controller associated with a power supply determines a first ratio value. The first ratio value may be a ratio of a second time duration with respect to a first time duration, where the second time duration is a measured time duration associated with demagnetizing of a transformer in a first control cycle. The first time duration may be a measured time duration of activating a first switch in the first control cycle, where activation of the first switch operative to control a magnitude of primary current through a primary winding of the transformer. For second control cycle occurring subsequent to the first control cycle, the controller calculates an ON-time duration for activating the second switch based on the determined first ratio value.

1 . An apparatus comprising:
 first switch circuitry including a first node and a second node, the first node operative to receive first current, the first switch circuitry operative to control conveyance of the first current received at the first node through the first switch circuitry and out the second node of the first switch circuitry; and   a monitor circuit operative to: i) receive a first signal outputted from a third node of the first switch circuitry, and ii) produce a second signal indicative of a magnitude of the first current.   
     
     
         2 . The apparatus as in  claim 1 , wherein the first signal is second current: i) received at the first node of the first switch circuitry, ii) conveyed through the first switch circuitry during a condition in which the first switch circuitry is ON, and iii) outputted from the third node to the monitor circuit. 
     
     
         3 . The apparatus as in  claim 2 , wherein a magnitude of the second current is proportional to a magnitude of the first current. 
     
     
         4 . The apparatus as in  claim 1 , wherein the first switch circuitry is a cut-off switch or protection switch, control of the first switch circuitry operative to disconnect an inverter from a battery source during a condition in which the first switch circuitry is operated in an OFF-state. 
     
     
         5 . The apparatus as in  claim 1 , wherein the first signal is a second current proportional to the first current; and
 wherein the monitor circuit is operative to produce the second signal based on a voltage produced by flow of the second current through a resistor.   
     
     
         6 . The apparatus as in  claim 5 , wherein the monitor circuit includes an analog-to-digital converter operative to convert the voltage into a digital value indicative of a magnitude of the first current. 
     
     
         7 . The apparatus as in  claim 1 , wherein the first signal is a second current in which a magnitude of the second current is proportional to a magnitude of the first current; and
 wherein the monitor circuit includes an amplifier circuit operative to: i) convert the second current into a voltage signal, and ii) apply an offset to the voltage signal.   
     
     
         8 . The apparatus as in  claim 7 , wherein the monitor circuit further includes:
 filter circuitry to filter the voltage signal; and   an analog-to-digital converter operative convert the filtered voltage signal into a digital value indicative of a magnitude of the first current.   
     
     
         9 . The apparatus as in  claim 1 , wherein the first switch circuitry is disposed in series with second switch circuitry; and
 wherein the second switch circuitry is operative to control conveyance of the first current through at least one winding of a motor.   
     
     
         10 . The apparatus as in  claim 9 , wherein the second switch circuitry is operative to receive the first current from a voltage source and output the first current to the first node of the first switch circuitry. 
     
     
         11 . The apparatus as in  claim 10  further comprising:
 a capacitor disposed in parallel with the second switch circuitry; and 
 wherein a combination of the capacitor and the second switch circuitry is disposed in series with the first switch circuitry. 
 
     
     
         12 . The apparatus as in  claim 10  further comprising:
 a capacitor disposed in parallel with a series combination of the first switch circuitry and the second switch circuitry. 
 
     
     
         13 . The apparatus as in  claim 9 , wherein the first switch circuitry is operative to receive the first current at the first node from a voltage source and supply the first current through the second node to the second switch circuitry. 
     
     
         14 . The apparatus as in  claim 13  further comprising:
 a capacitor disposed in parallel with the second switch circuitry; and 
 wherein a parallel combination of the capacitor and the second switch circuitry is disposed in series with the first switch circuitry. 
 
     
     
         15 . The apparatus as in  claim 13  further comprising:
 a capacitor disposed in parallel with a series combination of the first switch circuitry and the second switch circuitry. 
 
     
     
         16 . The apparatus as in  claim 1 , wherein the first switch circuitry includes:
 a first switch including a first gate node, a first drain node, and a first source node;   a second switch including a second gate node, a second drain node, and a second source node;   an operational amplifier;   wherein the first gate node is directly connected to the second gate node;   wherein the first drain node is directly connected to the second drain node;   wherein the operational amplifier is operative to generate the first signal outputted from the third node of the first switch circuitry based on a first voltage at the first source node and a second voltage at the second source node.   
     
     
         17 . The apparatus as in  claim 16 , wherein the operational amplifier is configured to operate in a buffer mode in which an output of the operational amplifier is directly connected to the second source node. 
     
     
         18 . A controller operative to control operation of: i) the first switch circuitry as in  claim 1 , and ii) second switch circuitry directly coupled to the first switch circuitry. 
     
     
         19 . A method comprising:
 receiving a first signal outputted from first switch circuitry, the first switch circuitry including a first node and a second node, the first switch circuitry operative to control conveyance of first current received at the first node of the first switch circuitry through the first switch circuitry and out the second node of the first switch circuitry, the first signal received from a third node of the first switch circuitry; and   converting the received first signal into a second signal indicative of a magnitude of the first current.   
     
     
         20 . The method as in  claim 19 , wherein the first signal is second current: i) received at the first node of the first switch circuitry, ii) conveyed through the first switch circuitry, and iii) outputted from the third node to the monitor circuit.